Applications for the Active Filter Board include being used as an anti-aliasing filter for A/D conversion or as a reconstruction filter after D/A conversion.

The Active Filter Board is configured as a two-pole active filter followed by a third passive pole if desired. The op-amp circuitry forms the two-pole filter while the RC network at the output of the operational amplifier forms the third passive pole.

The operational amplifier used for this board is the Texas Instruments OPA172 whose main features make it suitable for experimenting.

These features are:

Wide Supply Range: +4.5V to +36V, ±2.25V to ±18V

Low Offset Voltage: ±0.2mV

Gain Bandwidth: 10 MHz

Input Range Includes the Negative Supply

Input Range Operates to Positive Supply

Rail-to-Rail Output

Low Noise: 7nV/√Hz

High Common-Mode Rejection: 120 dB

Low Input Bias Current: ±8pA

Low Quiescent Current: 1.6mA per Amplifier

For your convenience, the board comes bundled with some components that you can put into the sockets — two 15KΩ resistors, a 3KΩ resistor, a 750Ω resistor, a 10KΩ resistor, a 0.1µF capacitor, a 0.033µF capacitor, and a 0.01µF capacitor. See the User Manual and Bill of Materials for typical socket placement. Between the sockets are solder pads in case you want to install SMD components instead.

The User Manual shows you which component values to place where to create Butterworth, Bessel, and 3-dB Chebyshev type low-pass filters, as well as how to calculate new corner frequency values. Using that information, it is easy to make active anti-aliasing and reconstruction filters.

Male headers provide access to the power pins.

The Active Filter Board can be operated with single or dual power supplies, and the 10MHz bandwidth makes it sufficient for most experimental circuits.

Connect multiple Schmartboards together!

Every Schmartboard has small notches along its sides which allow you to connect any number of them together in any combination. Purchase a set of the Mechanical Bridge Interconnects available in the options below if you want to be able to combine your Schmartboards.